Near-planar light outcoupling structures with finite lateral dimensions for ultra-efficient and optical...

The stratified structure of organic light-emitting diodes (OLEDs) confines much of the generated light within substrates or organic layers, limiting outcoupling to air. Macroscale half-ball lenses extract most substrate-trapped light but compromise the inherent planarity of OLEDs, while microlens arrays (MLAs), only tens of micrometres tall, preserve planarity yet provide only modest enhancements, particularly with limited lateral dimensions. Here, we introduce a systematic strategy to enhance outcoupling while maintaining near-planarity. By jointly tailoring the OLED device stack and the topography of near-planar outcoupling structures, we overcome the limited prompt extraction responsible for the modest performance of conventional MLAs. Our optimized devices reach an external quantum efficiency of 48.0% and a current efficiency of 192 cd A⁻¹, surpassing bare OLEDs (35.6%, 102 cd A⁻¹) and MLA-attached OLEDs (35.4%, 150 cd A⁻¹). This approach addresses trade-offs among intrusiveness, aperture ratio, and performance, providing a promising route to ultra-efficient, optical-crosstalk-free OLED displays.